For those who don't know the story, this is an orchid that Darwin saw in Madagascar (well, maybe not this exact one, but something like it). The flower has a long, slim tube that sticks out the back of it and hangs down (yellowish green in this photo), and has nectar at the end of it. Darwin hypothesized that the pollinator of the flower was a moth or a butterfly with a long tongue. That moth was discovered -- 60 years after Darwin died.